This invention relates to a silver-free radiation-sensitive material for direct optical recordings.
Numerous processes which operate on the basis of perhalides and dyestuff precursors already exist (R. H. Spraque and coworkers: Phot. Sci. Eng. 5 98 (1961), 8 91 (1963), 8 95 (1965), A. Fotland. J. Phot. Sci. 18 33 (1970) DE-OS No. 2 241 563, DE-OS No. 2 055 872, DE-OS No. 2 142 966). All these processes involve color-promoting processes, i.e. dyestuffs are produced from dyestuff precursors and perhalides under the action of light after executing complicated chemical processes. The sensitivity of such systems can be increased by the addition of sensitizers (DE-OS No. 2 142 966).
Up to now, the most favorable material qualities have been attained with some spirobipyranes. However, these compounds also present some serious disadvantages, such as other compounds, for instance leucobases of the triarylmethane dyestuffs and styryl dyestuff bases. Here, the low resistance of most dyestuff bases to light and thermal influences should especially be considered. Furthermore, it is difficult to color over the whole visible spectrum with a dyestuff base. Last but not least, many dyestuffs or their precursors can only be produced through complicated, protracted syntheses.
It is the task of this invention to improve treatment qualities of silver-free recording materials.
The known materials for optical development have the disadvantage that they are spectrally limited and unstable and that the synthesis of dyestuff precursors is costly and complicated. It is, therefore, the task of the present invention to create a stable, silver-free recording material with high sensitivity and large dissolving capacity, whose coloring substances are easy to synthesize and present a wide spectrum of colors.